The Tao Of ASICs

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Wednesday, June 03, 2009

In one of my earlier posts (EDA Standards I'd Love To See) , I argued for a standard for interconnect extraction rule from that will be used by the extraction tool. I quote:

"There are only so many things one expects to be present in an RC Deck. These values, much like in DRC decks, are constant for a given process. It can't be hard to develop a common extraction rules format. Vendors can still add value via the speed and accuracy of their RC estimation algorithms."

TSMC has now developed a common RC extraction deck format called iRCX that can be used as the input for all RC extraction tools. The utopian promise: RC tools all support the same standard for rules and compete on accuracy and runtime. According the press release, this standard is the first of many to come (I' m expecting that DRC & LVS rule formats are next in line).

Sunday, March 29, 2009

A physicist and a mathematician setting in a faculty lounge.Suddenly, the coffee machine catches on fire. The physicist grabs abucket and leaps towards the sink, fills the bucket with water andputs out the fire. The second day, the same two sit in the samelounge. Again, the coffee machine catches on fire. This time, themathematician stands up, gets a bucket, hands the bucket to thephysicist, thus reducing the problem to a previously solved one.

My interpretation: Make the physicist do all the work!

There any many problems is ASIC design for which straightforward solutions/tools may not exist. You want the tool to consider timing, area, power and X. The rub is that the tool does not support measuring or optimizing for X. In such cases, it is worthwhile to explore the possibility of reframing X into something the tool does understand.

You don't create a tool that optimizes only X and spend time iterating between X optimization and standard optimization

You get to leverage the powerful algorithms built into your EDA tool to concurrently optimize for timing, area, power, X, Y, Z, ...

For example, if X is uniform placement density and the tool does not explicitly support it, you can recast the problem as one of uniform/max/min metal density (which is supported via the DRC engine). Using virtual (user-created) metal layers and associated density rules to represent the placement density, enhance the cell's physical view such that the tool sees that the entire area of the cell is covered with one big piece of virtual metal. During optimization, the tool will try and meet the virtual layer density requirements (representative of uniform placement density) along with its standard cost functions (area, timing, power,etc).